This invention relates to the field of ozone synthesis. It presents a new operating process and apparatus for producing ozone from an oxygen-rich gas on a continuous basis, as required for many industrial oxidation demands, such as manufacture of peroxides and organic acids, treatment of municipal sewage and manufacturing wastes, large-scale disinfection and odor control applications, bleaching and treatment of potable water. Advantages have been found in the use of clean dry oxygen-rich gas for ozone synthesis as compared to air. A silent electric discharge type ozonizer will produce more than twice the amount of ozone using oxygen feed, thereby reducing the capital cost of corona generating equipment. The energy required to produce a given weight of ozone product is decreased by more than half whereby the operating cost for the generator is reduced. Also, the maximum ozone concentration obtainable is increased by about the same factor employing 90% + oxygen purity.
The cost of producing the oxygen -rich feedstream for a continuous ozone generating plant is sufficiently high that most of the oxygen passed through the ozone generating equipment must be recovered and recycled to make the process economical. A method for recovering and recycling ozone has been described by Kiffer in U.S. Pat. No. 2,872,397. According to this prior art system, oxygen in a relatively pure form is converted by electric discharge reactor into ozone and the resulting gas mixture containing a major fraction of oxygen and a minor fraction of ozone is passed through a bed of adsorbent particles, such as silica gel. The ozone is adsorbed by silica gel and the remaining oxygen is passed through the bed for recovery and recycle. The recycle stream is replenished continuously or periodically with oxygen in an amount to compensate for that which is converted to ozone product in the generator. Typically, two or more adsorption units are employed so that when the adsorbent silica gel in one vessel reaches the saturation point for ozone capacity the ozone containing gas may be switched to other adsorption units. While the ozone-containing oxygen-rich stream from the ozone generator is being treated in the second adsorption unit, the ozone in the first unit is being removed from the adsorbent using a stripping gas such as air, nitrogen or other diluent gas which acts as a carrier for the ozone. This results in a safe ozone-carrier gas mixture suitable for subsequent chemical reaction without explosion hazards inherent in oxygen-ozone mixtures. The adsorption temperatures according to prior art methods may be about -80.degree.C to +20.degree.C. It is known that the adsorption capacity of silica gel decreases markedly as temperature approaches ambient.